The DTC/DTCC clears transactions. Sometimes adjustments are made which can be merely clerical or other things like stock loans et al. Security lending tends to be a big part of this...so it may have possibly been a very ill advised short position that was closed out.
If an individual initiated a short position... it would have cleared @ DTC and shown as an increase in shares held via DTC. When said individual closed position..those same shares would be removed from the DTC.
That is just one example of how the DTC/DTCC makes adjustments. You can find examples of how to make adjustments via the DTC web site. Have fun :)
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